Australian Prime Minister Tony Abbott said on Monday there was no time limit on the hunt for Malaysia Airlines Flight MH370, missing for more than three weeks in the Indian Ocean with 239 people on board.

"I'm certainly not putting a time limit on it," Abbott told reporters at Pearce airbase in Perth. "We can keep searching for quite some time to come and we will keep searching for quite some time to come."

"The intensity of our search and the magnitude of operations is increasing, not decreasing," he said.

A total of 20 aircraft and ships will be scouring the remote seas off the Australian southwest coast on Monday.

Abbott's remarks came a day after U.S. Navy officials suggested on Sunday the search for the aircraft, which went missing more than three weeks ago and is presumed to have crashed, could go on for years.

The chief of the China Maritime Search and Rescue Center, He Jianzhong, told the Xinhua state news agency no objects linked to the plane had been found on Sunday, and that Chinese vessels would expand their search area.

Numerous objects have been spotted in the two days since Australian authorities moved the search 1,100 km (685 miles) after new analysis of radar and satellite data concluded the Boeing 777 traveled faster and for a shorter distance after vanishing from civilian radar screens on March 8. None has been confirmed as coming from Flight MH370.

U.S. Navy Captain Mark Matthews, who is in charge of the U.S. Towed Pinger Locator (TPL), told journalists at Stirling Naval Base near Perth that the lack of information about where the plane went down seriously hampers the ability to find it.

"Right now the search area is basically the size of the Indian Ocean, which would take an untenable amount of time to search," he said.

"If you compare this to Air France flight 447, we had much better positional information of where that aircraft went into the water," he said, referring to a plane that crashed in 2009 near Brazil and which took more than two years to find.

The U.S. Navy cannot use the pinger locator and other sonar used to listen for the beacons on the aircraft's flight data and cockpit voice recorders until "conclusive visual evidence" of debris is found, U.S. Navy spokesman Commander William Marks told CBS' "Face the Nation" program.

If no location is found, searchers would have to use sonar to slowly and methodically map the bottom of the ocean, he said. "That is an incredibly long process to go through. It is possible, but it could take quite a while," he said.

Among the vessels to join the search is an Australian defense force ship, the Ocean Shield, that has been fitted with a sophisticated U.S. black box locator and an underwater drone.

Australia, which is coordinating the search in the southern Indian Ocean, said it had established a new body to oversee the investigation and issued countries involved in the search a set of protocols to abide by should any wreckage be found.

Malaysia says the plane, which disappeared less than an hour into a flight from Kuala Lumpur to Beijing, was likely diverted deliberately. Investigators have determined no apparent motive or other red flags among the 227 passengers or the 12 crew.

WEATHER THREATENS EXPANDED SEARCH

The Australian Maritime Safety Authority (AMSA) said aircraft from China, Australia, Japan, South Korea, Malaysia and the United States were involved in the search on Sunday.

The search has involved unprecedented cooperation between more than two dozen countries and 60 aircraft and ships but has also been hampered by regional rivalries and an apparent reluctance to share potentially crucial information due to security concerns.

Asked if more resources could added to the international effort, U.S. Navy spokesman Marks told CBS, "We have about as many assets out there as we can. You have to wonder if the debris is even out there. If we fly over something, we will see it."

This week, Australia issued a set of rules and guidelines to all parties involved in the search, giving Malaysia authority over the investigation of any debris to be conducted on Australian soil, a spokeswoman at the Department of Foreign Affairs and Trade told Reuters.

"Australia intends to bring the wreckage ashore at Perth and hold it securely for the purposes of the Malaysian investigation," the spokeswoman said.

Australian Prime Minister Tony Abbott on Sunday appointed a former chief of Australia's defense forces, Air Chief Marshal Angus Houston, to lead a new Joint Agency Coordination Centre (JACC).

The JACC will coordinate communication between all international partners as well as with the families of passengers, many of whom are expected to travel to Perth.

FAMILY PROTESTS

The Malaysian government has come under strong criticism from China, home to more than 150 of the passengers, where relatives of the missing have accused the government of "delays and deception".

On Sunday, dozens of angry relatives of Chinese passengers from Beijing met with Chinese embassy officials in Kuala Lumpur, piling more pressure on the Malaysian government over its handling of the case.

"We arrived here this morning with sorrow and anxiety, because the special envoy from Malaysia, the so called high-level tech team, did not give us any effective information in meetings that took place in three consecutive days," said Jiang Hui, a relative of one of the victims.

"We want the Malaysian government to apologize for giving out confusing information in the past week which caused the delay in the search and rescue effort."